Previous analyses of the fossil record suggest that biodiversity tends to dip during warm, "greenhouse" phases of global temperature. Now, research published this week turns that conclusion on its head; a warming planet, it seems, may actually encourage variation in Earth's lifeforms.

But the rate of warming matters, as well — and that, note researchers, means that today's climate change could prove detrimental, yet.

The findings, which are published in this week's issue of Proceedings of the National Academy of Sciences, contradict those of an influential study published five years ago, which showed an inverse relationship between warmer climates and biodiversity. Contrasting results pop up with some frequency in the scientific literature, but what makes this situation particularly interesting is that the studies were conducted by the same research group — a team of scientists led by evolutionary ecologist Peter Mayhew.

Reports Nature's Richard Lovett:

The reason for the about-face, says Mayhew... is that the earlier work measured fossil diversity by tallying the first and last appearances of each group of species, then assuming that the creatures existed only during the intervening years. This might sound logical, but overlooks the fact that some geological periods are better studied than others.

This time around, Mayhew and his colleagues accounted for these gaps in the record by excluding them entirely. "And, instead of interpolating organisms' presence from origination and extinction dates," notes Lovett, the group "merely tallied species groups present during each [well-sampled geological period]."

"This control," write the researchers, "appears to reverse the temporal association between temperature and biodiversity, such that taxonomic richness increases, not decreases, with temperature."

So does that mean that today's rising temperatures will translate to a spike in global species richness? Not necessarily. Lovett explains:

Warming produces both extinctions and originations, and in the past the originations of new species have outstripped the loss of old ones, says Mayhew. But this does not mean that today's climate change will be beneficial.

"The rate of change is very important," Mayhew says. For diversity to rise, he explains, new species need to evolve. And that takes between thousands and millions of years - much slower than the rate at which extinctions are likely to occur with today's rapid change.